Radiation curable inks and coatings containing diacetone acrylamide

ABSTRACT

The present invention provides a radiation curable printing/coating composition comprising an acrylamide material, preferably diacetone acrylamide, which is very effective in providing fast curing, impact resistance, extensibility, thermal/storage stability with respect to yellowing and odor, free from VOC solvents, that also has excellent adhesion properties.

This application claims priority to Provisional Application Nos. 61/977,787, filed Apr. 10, 2014, and 61/945,956, filed Feb. 28, 2014, both of which are hereby incorporated herein in their entirety.

FIELD OF THE INVENTION

The present invention is directed to radiation curable ink and coating compositions that have good cure speed, conversion, and cured film hardness. The inks and coatings of the invention show a reduced tendency for substrate embrittlement, ink film softening, or loss of adhesion when applied in multiple layers. The inks and coatings of the invention also have good flexibility and extensibility. In addition, compared to prior art inks and coatings, the energy curable inks and coatings show a reduced tendency to thermally yellow or change on storage, reduced unpleasant odor, and less swelling of printing components, such as squeegee rubbers used in screen printing.

BACKGROUND

Compositions may be applied using various print presses/machines, onto to a variety of substrates to fulfill many different market requirements. Printing compositions may be formulated containing mainly multi-functional monomers, with multi-substrate adhesion and fast curing properties, however, they may embrittle plastic substrates and are not extensible at room or elevated temperatures. Alternative formulations low in functionality may be insufficiently reactive when exposed to radiation, producing soft films, particularly in multi-layer applications. The properties of N-vinyl caprolactam are unusual in producing fast curing films with reduced tendency to the above problems. These compositions, based on N-vinyl caprolactam, are capable of adhesion to a range of substrates, while retaining impact resistance, extensibility and adhesion of multi-layer prints.

The continued use of N-vinyl caprolactam is undesirable, due to toxicological concerns and product labeling. The tertiary acrylamide monomer N-acryloyl morpholine (ACMO) has been used as an alternative, but above 10% it carries similar labeling to N-vinyl caprolactam, it is a severe eye irritant with limitations on its global registration.

Radiation curable coatings may embrittle plastic substrates, via a crack propagation mechanism, where a crack initiated in the more brittle coating propagates across the boundary to the underlying substrate. The reduction in impact resistance depends critically on the nature and thickness of the radiation cured coating and the nature and thickness of the underlying plastic. Good bonding is necessary between the coating and the substrate layer to propagate the crack. Hence a brittle coating, when subjected to an impact, might crack itself and flake off where adhesion is poor, or crack the underlying substrate if adhesion good. In display and some industrial printing, several layers of ink may be deposited, on one or both sides of the substrate. The problem is worse with screen applied layers, which are much thicker than other printing processes, and the multi-layer build may be perhaps 40 microns in thickness on a single side. Additionally, the crosslinking of ink layers may continue after printing, increasing the tendency to embrittle the substrate as a function of time. Some formulators have tried to improve substrate adhesion and plasticize ink films by the inclusion of solvents and/or non-reactive plasticizers in printing compositions, which may give rise to flash-point problems and film softening due to the presence of unreacted materials. This softening is particularly apparent in multi-layer prints. The printing compositions described herein are preferably free of these additives.

In printing ink compositions for automotive and membrane switch applications the coating film requires impact resistance, and extensibility, both at room and elevated temperature. In narrow web, screen and flexographic applications there has been a trend to stiffer thinner substrates, which may be embrittled by printed layers and can split or fracture when flexed or even while printing on the web. The solutions to all the above problems require formulations with sufficiently low overall crosslink density for the particular application.

Radiation curable coating or printing compositions may be yellowed by included components or on exposure. Some photoinitiators are initially yellow and on exposure and aging may darken further. Other initiators have much lower yellowing when exposed to radiation (UV light), but may yellow on ageing at ambient or elevated temperature due to thermal oxidation of breakdown products. Monomers and oligomers may also yellow on exposure to radiation, both initially, and thermally on storage. Thermal processes may also darken compositions on storage in the pot. Aged samples, when printed, cured, and stored, have an increased tendency to yellow. Yellowing is very important and undesirable in whites, varnishes, light colors and process inks. Ink or coating compositions would preferably have a long shelf life of 12 months or greater, and formulations containing N-vinyl caprolactam show considerable yellowing when stored at ambient conditions. The yellowing is also important in outdoor applications where lifetime may be reduced.

Automotive and membrane switch printed parts may have a very long working life up to and above 10 years, and to simulate these conditions, the coatings must survive extended accelerated testing, for example 7 days at 105° C. N-vinyl caprolactam is a solid at room temperature and needs to be melted for incorporation, and is therefore often stored at elevated temperature. It has a strong tendency to yellow or brown on aging and also yellows on exposure to radiation and subsequent storage at room temperature or above. It is very difficult to prevent these problems even with thermal stabilizers.

In white ink compositions, there have been attempts to mask these yellowing effects by the addition of violet or blue toners, or combinations, and/or optical brighteners. This is not an ideal solution and the colored toners often float or separate on storage in the container and must be re-mixed prior to use.

During the screen printing process in both flat-bed and rotary applications, the printing composition is squeezed through the mesh by the squeegee. Components of the printing composition, both monomers and initiators, may individually or combined cause various types of squeegee rubbers to swell. Different grades and types have varying susceptibility to swelling and damage. The swelling may cause print defects like streaking, and, in extreme cases, small pieces may break off, damaging the mesh. Combinations of components may worsen or lessen squeegee attack. Monofunctional monomers like N-vinyl caprolactam, tetrahydrofurfuryl acrylate, and acrylol morpholine are particularly bad and their concentration may be limited by the severity of the effect. The deformed squeegee has to be replaced and this represents an additional cost to the customer. Flexographic ink compositions containing mono-functional monomers often swell printing plates more than multi-functional monomers, and N-vinyl caprolactam is particularly poor in this respect.

WO 2006/041004 (GB 2435044) discloses UV curable inkjet compositions that comprising an acrylamide with trifunctional or higher acrylate monomers. Preferred compounds are typically tertiary acrylamides such as N,N′-dialkylamino acrylamides or ACMO.

EP 2644664 provides an actinic radiation curable type composition for use in an in-mold molded article, including an ink jet recording method, decorative sheet, decorative sheet molded product, a process for producing an in-mold molded article, and an in-mold molded article. The composition includes at a minimum an oligomer, an acrylamide derivative, and an N-vinyl compound. The document describes N-vinyl lactams, particularly N-vinylcaprolactam (NVC), as preferred components of the composition. NVC has a relatively high odor on cure and a poor toxicological profile. The examples include formulations that contain high levels of N-vinyl caprolactam and 2-ethoxyethoxyethyl acrylate (EOEOEA), which carry adverse product labeling, and high levels of the monomer dicyclopentanyl methacrylate (Fancryl FA-513M), which has a very unpleasant odor.

EP 2302007 is directed to ink compositions that include photoinitiators containing a 4-thiophenyl substituted benzophenone group within the structure. Although a further definition of polymerizable compounds that can be used in the formulation include acrylamides, only NVC is used in the working examples. NVC is the preferred compound. Compounds of the examples contain high levels of NVC, EOEOEA, tetrahydrofurfuryl acrylate (THFA), or dicyclopentenyloxyethyl acrylate (Fancryl FA-512A), all of which have an extremely unpleasant odor and/or carry adverse toxicological labeling.

EP 250622 describes ink compositions comprising acrylamides. The document defines a series of multi-functional acrylamides (including diacetone acrylamide) which can be used in conjunction with other acrylamides. However, the patent is directed to water-dilutable formulations, with water being a necessary part of the formulation. There are no options for using acrylate monomers within the chemistry described in the application.

U.S. Pat. No. 7,297.460 describes inkjet inks that contain polyhedral oligomeric silesquioxane (POSS), optionally substituted with secondary acrylamide or methacrylamide functional groups. The description does not refer to the use of low molecular weight acrylamides. All acrylamide compounds described are acrylamide functional POSS.

EP 0337705 describes screen printing inks consisting of a water soluble radiation curable component, a photoinitiator and/or a photochemical crosslinking agent, a pigment and/or a water soluble dye, and an ionic, non-radiation curable thickener. NVP is used as a water-soluble unsaturated monomer in the working examples. The document describes inks that have high screen stability without compromising cure speed, combined with a low printed film weight comparable to solvent based inks. The inks of EP 0337705 must contain 20-80 wt % water at the time of printing. If made in concentrated form, they must be diluted with water prior to use for printing.

U.S. Pat. No. 4,789,621 discloses emulsions used to coat screens for screen printing. After application to the screen, to form a film covering all of the mesh holes, a blocking material (i.e. stencil) is placed on the emulsion film in the non-image areas to be printed. The emulsion is cured, blocking the screen holes in the screen mesh so that in the cured areas, no ink can penetrate. The emulsions are based on polyvinyl alcohol, and polyvinyl acetate or polyvinyl acetate copolymers, to which are added diacetone acrylamide and acrylic monomers. Di- or higher functional acrylic monomers are preferred. The emulsions are water-based, allowing for easy removal of the non-cured portions of the emulsion to produce the pattern on the screen mesh through which ink will be applied to the substrate. The viscosity of the emulsions is 20,000 to 30,000 cps (i.e. 20 to 30 Pa s) at 25° C., and are therefore not suitable as inks.

JP 59054600 and JP 50036204 provide water-based resin compositions for the preparation of printing plates (photosensitive and flexographic).

WO 2010/150,023 discloses a UV ink that is curable by exposing the ink to UV radiation from an LED source, followed by UV radiation from a flash lamp. The application describes a UV ink that contains an N-vinyl amide or an acrylamide (N-acryloyl amides), and defines ACMO as preferred. The working examples contain only NVC as an amide compound of this type.

WO 2008/093071 describes the use of cyclic monofunctional acrylate monomers in inkjet ink. Reference is made to the use of N-vinyl amides and acrylamides (N-acryloyl amides), and defines ACMO as the preferred example. No acrylamide monomers of any kind are supported by practical examples.

WO 2008/117,092 discloses use of an inkjet formulation that is resistant to blocking on a reel. Reference is made to the use of N-vinyl amides and acrylamides (N-acryloyl amides), and defines ACMO as preferred. All the examples are based on NVC. As discussed above, NVC has an unpleasant odor and adverse toxicological profile.

The commercial monomer N-vinyl caprolactam has recently changed hazard classification, and, by agreement with EuPIA, Sun Chemical is obliged to remove this material from formulations. N-vinyl caprolactam (NVC) is generally regarded as a unique monomer with no alternatives. The closest commercial alternative is ACMO, which itself has an undesirable hazard classification, particularly when used at over 10%.

Prior art inks and coatings may have good performance on some of the desired properties. But each, while being good in some properties, lack in others. Thus, there is a need to provide radiation curable inks and coatings that avoid the use of disfavored components such as NVC, while still maintaining desirable properties, particularly when used in multi-layer builds.

SUMMARY OF THE INVENTION

The present invention provides radiation curable ink or coating compositions that are very effective in providing fast curing, impact resistance, extensibility, thermal/storage stability with respect to yellowing and odor, free from VOC solvents, and also have excellent adhesion properties. The compositions of the invention comprise an acrylamide material, preferably diacetone acrylamide.

In a certain aspect, the present invention provides a radiation curable printing ink or coating composition comprising:

-   -   a) 1-60% wt. of an acrylamide material or blends thereof,         wherein at least a portion of the acrylamide material is         diacetone acrylamide;     -   b) 1-60% wt. of an additional monofunctional acrylate or         methacrylate monomer or blends thereof;     -   c) 0-20% wt. of a difunctional acrylate or methacrylate monomer         or blends thereof;     -   d) 0-10% wt. of a trifunctional or higher acrylate or         methacrylate monomer or blends thereof;     -   e) 0-60% wt. of a mono or multifunctional acrylate or         methacrylate oligomer or blends thereof;     -   f) 0-40% wt. of additional reactive oligomers or resins;     -   g) 0-40% wt. of additional inert oligomers or resins;     -   h) 0-25% wt. of a photoinitiator or blends thereof;     -   i) 0-5% wt. water; and     -   j) 0-5% wt. solvent;         wherein, the composition contains a maximum of 5% wt. N-vinyl         compounds; and wherein the composition contains no N-vinyl         caprolactam, N-vinyl pyrrolidone, or N-acryloyl morpholine.

In other embodiments, the majority of the acrylamide material present in the composition is diacetone acrylamide.

In other embodiments, all of the acrylamide material present in the composition is diacetone acrylamide.

In certain embodiments, the composition contains no N-vinyl compounds.

In certain embodiments, the additional monofunctional acrylate or methacrylate monomer comprises a cyclic mono-functional (meth)acrylate, with the cyclic radical being either saturated or unsaturated, including aromatic.

In other embodiments, the additional monofunctional acrylate or methacrylate monomer is selected from the group consisting of phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), isobornyl acrylate (IBOA), t-butyl cyclohexyl acrylate, 3,3,5-trimethyl cyclohexyl acrylate, tetrahydro-furfuryl acrylate (THFA), or mixtures thereof.

In certain embodiments, the composition contains no added water.

In certain embodiments, the composition contains monofunctional monomers in an amount of 1-45% wt.

In certain embodiments, the composition contains difunctional or higher monomers in an amount of 0-15% wt.

In certain embodiments, the composition contains a photoinitiator in an amount of 0.1-20% wt.

In certain embodiments of the composition, the acrylamide material is present an amount of 1-40% wt.

In other embodiments, the acrylamide material is present in an amount of 1-30% wt.

In other embodiments, the acrylamide material is present in an amount of 1-20% wt.

In other embodiments, the acrylamide material is present in an amount of 1-10% wt.

In other embodiments, the acrylamide material is present in an amount of 1-5% wt.

In certain embodiments, the composition further comprises a colorant or filler.

In certain embodiments, the composition further comprises one or more additives selected from the group consisting of stabilizers, surfactants, defoamers, slip additives, waxes, wetting additives and synergists.

In certain embodiments, the composition is a screen printable ink or coating, and is suitable for flat-bed or rotary screen printing.

In certain embodiments, the composition that is a screen printable ink or coating suitable for flat-bed or rotary screen printing has a viscosity in the range 0.2-2.5 Pa s, measured on a cone and plate viscometer at 25° C.

In certain embodiments, the composition is a flexographic ink or coating.

In certain embodiments, the composition that is a flexographic ink or coating has a viscosity in the range 0.2-1.0 Pa s, measured on a cone and plate viscometer at 25° C.

In certain embodiments, the composition is a gravure, pad or spray ink or coating.

In certain embodiments, the composition that is a gravure, pad or spray ink or coating has a viscosity in the range 0.01-0.2 Pas measured on a cone and plate viscometer at 25° C.

In certain embodiments, the radiation curable printing/coating composition, when cured, is impact resistant, extensible, and has good adhesion to a range of substrates, as well as previously printed layers of the composition when printed in multiple layers.

In certain embodiments, the radiation curable printing/coating composition has good storage stability with respect to yellowing and odor generation.

In certain embodiments, the radiation curable printing ink or coating composition causes little or no swelling of ink printing components, particularly rubber squeegees, plates, rollers etc.

In a certain aspect, the present invention provides a method of making an energy curable printing ink or coating composition comprising mixing:

-   -   a) 1-60% wt. of an acrylamide material or blends thereof,         wherein at least a portion of the acrylamide material is         diacetone acrylamide;     -   b) 1-60% wt. of an additional monofunctional acrylate or         methacrylate monomer or blends thereof;     -   c) 0-20% wt. of a difunctional acrylate or methacrylate monomer         or blends thereof;     -   d) 0-10% wt. of a trifunctional or higher acrylate or         methacrylate monomer or blends thereof;     -   e) 0-60% wt. of a mono or multifunctional acrylate or         methacrylate oligomer or blends thereof;     -   f) 0-40% wt. of additional reactive oligomers or resins;     -   g) 0-40% wt. of additional inert oligomers or resins;     -   h) 0-25% wt. of a photoinitiator or blends thereof;     -   i) 0-5% wt. water; and     -   j) 0-5% wt. solvent;         wherein, the composition contains a maximum of 5% wt. N-vinyl         compounds; and wherein the composition contains no N-vinyl         caprolactam, N-vinyl pyrrolidone, or N-acryloyl morpholine.

In a certain aspect, the present invention provides a printed article comprising the radiation curable ink or coating composition as described above.

Diacetone acrylamide is an alternative material found which gives fast curing as part of monofunctional monomer containing printing/coating compositions. Unlike many acrylamide compounds, it also has very favorable toxicology and a low hazard classification based on toxicology from its widespread commercial use in water-based emulsion polymer formulations. Compositions of the invention comprising diacetone acrylamide are fast radiation curing compositions, capable of multi-layer build without substrate embrittlement or adhesion failure. Additionally, these compositions exhibit low ultraviolet (UV), thermal and UV thermally induced yellowing, in can or on print storage, combined with low initial and aged odor development. It also exhibits reduced swelling of print application components like squeegees compared with other monomers like N-vinyl caprolactam, N-acryloyl morpholine and tetrahydrofurfuryl acrylate. These properties make it a suitable alternative to N-vinylcaprolactam, with superior properties outlined above, and with improved health and safety and EuPIA compliance.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of any subject matter claimed.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which the inventions belong. All patents, patent applications, published applications and publications, websites and other published materials referred to throughout the entire disclosure herein, unless noted otherwise, are incorporated by reference in their entirety for any purpose.

In this application, the use of the singular includes the plural unless specifically stated otherwise. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

In this application, the use of “or” means “and/or” unless stated otherwise.

As used herein, the terms “comprises” and/or “comprising” specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Furthermore, to the extent that the terms “includes,” “having,” “has,” “with,” “composed,” “comprised” or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”

As used herein, ranges and amounts can be expressed as “about” a particular value or range. “About” is intended to also include the exact amount. Hence “about 5 percent” means “about 5 percent” and also “5 percent.” “About” means within typical experimental error for the application or purpose intended.

As used herein, the term “monofunctional acrylate monomer” refers to a monomer containing one functional acrylate group.

As used herein, the term “multifunctional acrylate monomer” refers to a monomer having two or more functional acrylate groups.

As used herein, the term “difunctional acrylate monomer” refers to a monomer containing two functional acrylate groups.

As used herein, the term “trifunctional acrylate monomer” refers to a monomer containing three functional acrylate groups.

As used herein, the term “or higher” when referring to an acrylate monomer means a monomer containing greater than three functional acrylate groups.

As used herein, the terms “(meth)acrylate” or “(meth)acrylic acid” include both acrylate and methacrylate compounds.

Throughout this disclosure, all parts and percentages are by weight (wt % or mass % based on the total weight) and all temperatures are in ° C. unless otherwise indicated.

In a certain aspect, the present invention provides a radiation curable printing ink or coating composition comprising:

-   -   a) 1-60% wt. of an acrylamide material or blends thereof,         wherein at least a portion of the acrylamide material is         diacetone acrylamide;     -   b) 1-60% wt. of an additional monofunctional acrylate or         methacrylate monomer or blends thereof;     -   c) 0-20% wt. of a difunctional acrylate or methacrylate monomer         or blends thereof;     -   d) 0-10% wt. of a trifunctional or higher acrylate or         methacrylate monomer or blends thereof;     -   e) 0-60% wt. of a mono or multifunctional acrylate or         methacrylate oligomer or blends thereof;     -   f) 0-40% wt. of additional reactive oligomers or resins;     -   g) 0-40% wt. of additional inert oligomers or resins;     -   h) 0-25% wt. of a photoinitiator or blends thereof;     -   i) 0-5% wt. water; and     -   j) 0-5% wt. solvent;         wherein, the composition contains a maximum of 5% wt. N-vinyl         compounds; and wherein the composition contains no N-vinyl         caprolactam, N-vinyl pyrrolidone, or N-acryloyl morpholine.

In a certain aspect, the present invention a method of making an energy curable printing ink or coating composition comprising mixing:

-   -   a) 1-60% wt. of an acrylamide material or blends thereof,         wherein at least a portion of the acrylamide material is         diacetone acrylamide;     -   b) 1-60% wt. of an additional monofunctional acrylate or         methacrylate monomer or blends thereof;     -   c) 0-20% wt. of a difunctional acrylate or methacrylate monomer         or blends thereof;     -   d) 0-10% wt. of a trifunctional or higher acrylate or         methacrylate monomer or blends thereof;     -   e) 0-60% wt. of a mono or multifunctional acrylate or         methacrylate oligomer or blends thereof;     -   f) 0-40% wt. of additional reactive oligomers or resins;     -   g) 0-40% wt. of additional inert oligomers or resins;     -   h) 0-25% wt. of a photoinitiator or blends thereof;     -   i) 0-5% wt. water; and     -   j) 0-5% wt. solvent;         wherein, the composition contains a maximum of 5% wt. N-vinyl         compounds; and wherein the composition contains no N-vinyl         caprolactam, N-vinyl pyrrolidone, or N-acryloyl morpholine.

The inclusion of the monomer diacetone acrylamide provides fast radiation curing printing compositions capable of multi-layer build without substrate embrittlement or adhesion failure. Additionally, these compositions exhibit low ultraviolet (UV), thermal and UV thermally induced yellowing, in can or on print storage, combined with low initial and aged odor development. It also exhibits reduced swelling of print application components like squeegees compared with other monomers like N-vinyl caprolactam, N-acryloyl morpholine and tetrahydrofurfuryl acrylate. These properties make it a suitable alternative to N-vinylcaprolactam, with superior properties outlined above, and with improved health and safety and EuPIA compliance. The properties of solid monomers like diacetone acrylamide (melting point 56° C.), are hard to predict or measure, as they have to be tested in blends with other monomers, which may or may not be stable. There are predictive models for solvents and solvent blends, but not for monomer, initiators, oligomers and their mixtures. Diacetone acrylamide has unique properties amongst the acrylamides, which are not predictable from its chemical structure.

Surprisingly, the present inventors discovered that the monomer diacetone acrylamide is capable of similar properties to NVC when incorporated into printing compositions, with the advantage of good thermal and storage stability with respect to yellowing and odor, coupled with low levels of print application component swelling, particularly screen printing squeegees.

Radiation curable printing compositions containing diacetone acrylamide may be applied by a number of processes to the substrate materials. The compositions must vary in viscosity and rheology in order to apply evenly and properly to these substrates during the printing process. Examples of the printing processes include screen printing (flat-bed, cylinder and rotary), flexographic and gravure. This is not a complete possible list and by suitable adjustments other coating/printing methods may be possible. Typical viscosities for screen printing measured on a cone and plate viscometer at 25° C. are in the range 0.5-2.5 Pas; flexographic 0.2-0.6 Pas; gravure 0.05-0.15 Pas; and coating/spraying 0.01-1.0 Pas.

The printing compositions of the present invention containing diacetone acrylamide, provide not only a viable replacement for N-vinyl caprolactam in terms of cure speed, adhesion, impact resistance and extensibility, but have low thermal and radiation cured/thermal yellowing, low initial and aged odor, and low print component swelling, particularly squeegees and flexographic plates.

The energy curable printing compositions of the present invention show a reduced tendency for substrate embrittlement, ink film softening or loss of adhesion in multi-layers, by virtue of good cure speed, conversion and cured film hardness. Flexibility and extensibility are maintained. Additionally the energy curing compositions show a reduced tendency to thermally yellow or change on storage, decreasing unpleasant odor, and less swelling of printing components, particularly squeegee rubbers.

The printing inks/coatings preferably contain 1-40% of an acrylamide material, such as diacetone acrylamide, more preferably 3-25%, and most preferably 5-15% along with other monofunctional or multifunctional acrylate monomers, oligomers, reactive and non-reactive resins and photo-initiators, the selection of which are dependent on the balance of properties being sought. Optionally, colorants, pigments or dyes may or may not be included, and other non-pigment solid fillers and waxes may also be included.

It is understood that the inks of the present formulation could contain virtually any raw materials that are compatible with energy curable ink systems. A partial list of some of the classes of materials that could be used to formulate the inks of the present invention included below.

Examples of suitable monofunctional ethylenically unsaturated monomers include, but are not limited to, the following: 2-(2-ethoxyethoxy)ethyl acrylate; 2-phenoxyethyl acrylate; 2-phenoxyethyl methacrylate; C₁₂-C₁₄alkyl methacrylate; C₁₆-C₁₈alkyl acrylate; C₁₆-C₁₈alkyl methacrylate; caprolactone acrylate; cyclic trimethylolpropane formal acrylate; ethoxylated (4) nonyl phenol acrylate; isobornyl acrylate; isobornyl methacrylate; isodecyl acrylate; lauryl acrylate; methoxy polyethylene glycol (350) monomethacrylate; octyldecyl acrylate; polypropylene glycol monomethacrylate; stearyl acrylate; tetrahydrofurfuryl acrylate; tetrahydrofurfuryl methacrylate; tridecyl acrylate; t-butyl cyclohexyl acrylate; 3,3,5-trimethyl cyclohexyl acrylate; 2-phenyl phenoxyethylacrylate; combinations thereof, and the like.

Examples of suitable polyfunctional ethylenically unsaturated monomers include, but are not limited to, the following: 1,3-butylene glycol dimethacrylate; 1,4-butanediol dimethacrylate; 1,6-hexanediol diacrylate; 1,6-hexanediol dimethacrylate; alkoxylated diacrylate; diethylene glycol dimethacrylate; dipropylene glycol diacrylate; ethoxylated (10) bisphenol-A diacrylate; ethoxylated (2) bisphenol-A dimethacrylate; ethoxylated (3) bisphenol-A diacrylate; ethoxylated (3) bisphenol-A dimethacrylate; ethoxylated (4) bisphenol-A diacrylate; ethoxylated (4) bisphenol-A dimethacrylate; ethoxylated bisphenol-A dimethacrylate; ethoxylated (10) bisphenol-A dimethacrylate; ethylene glycol dimethacrylate; polyethylene glycol (200) diacrylate; polyethylene glycol (400) diacrylate; polyethylene glycol (400) dimethacrylate; polyethylene glycol (600) diacrylate; polyethylene glycol (600) dimethacrylate; propyxylated (2) neopentyl glycol diacrylate; tetraethylene glycol diacrylate; tetraethylene glycol dimethacrylate; tricyclodecane dimethanol diacrylate; tricyclodecane dimethanol dimethacrylate; triethylene glycol diacrylate; triethylene glycol dimethacrylate; tripropylene glycol diacrylate; ethoxylated (15) trimethylolpropane triacrylate; ethoxylated (3) trimethylolpropane triacrylate; ethoxylated (6) trimethylolpropane triacrylate; ethoxylated (9) trimethylolpropane triacrylate; ethoxylated (5) pentaerythritol triacrylate; ethoxylated (20) trimethylolpropane triacrylate; propoxylated (3) glyceryl triacrylate; trimethylolpropane triacrylate; propoxylated (5.5) glyceryl triacrylate; pentaerythritol triacrylate; propoxylated (3) glyceryl triacrylate; propoxylated (3) trimethylolpropane triacrylate; trimethylolpropane triacrylate; trimethylolpropane trimethacrylate; tris-(2-hydroxy ethyl) isocyanurate triacrylate; di-trimethylolpropane tetraacrylate; dipentaerythritol pentaacrylate; ethoxylated (4) pentaerythritol tetraacrylate; pentaerythritol tetraacrylate; dipentaerythritol hexaacrylate; combinations thereof, and the like.

The inventive formulations may also contain oligomers and resins, both reactive and non-reactive (inert). The oligomers could include epoxy acrylates, polyurethane acrylates, polyester acrylates, polyether acrylates and acrylic acrylates, or their methacrylates. The non-reactive (inert) resins could include but are not limited to acrylics, aldehyde, ketone, vinyl, polyester, cellulose derivatives and hydrocarbon resins. This list of additive resins and oligomers is extensive, but not comprehensive, and represents only possible examples. Other examples and combinations remain within the scope and spirit of the invention. These materials may be present in the formulation in the range 0-40%, more frequently 0-20%.

Suitable photoinitiators include, but are not limited to, the following: α-hydroxyketones, including, but not limited to, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone; 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one; and 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone; acylphosphine oxides including, but not limited to 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; 2,4,6-trimethylbenzoyl-diphenyl phosphinate; and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and α-aminoketones including, but not limited to, 2-methyl-1-[4-methylthio)phenyl]-2-morpholinopropan-1-one; 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one; and 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one; combinations thereof, and the like.

Examples of other suitable photoinitiators include benzyl dimethyl ketal; thioxanthone initiators such as 2-4-diethylthioxanthone, isopropylthioxanthone, 2-chlorothioxanthone, and 1-chloro-4-propoxythioxanthone; benzophenone initiators such as benzophenone, 4-phenylbenzophenone, and 4-methylbenzophenone; methyl-2-benzoylbenzoate; 4-benzoyl-4-methyldiphenyl sulphide; phenylglyoxylate initiators such as phenyl glyoxylic acid methyl ester, oxy-phenyl-acetic acid 2-[2-hydroxyl-ethoxy]-ethyl ester, or oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester; titanocen radical initiators such as titanium-bis(η5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]; oxime ester radical initiators such as [1-(4-phenylsulfanylbenzoyl)heptylideneamino]benzoate, or [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]-ethylideneamino]acetate; plus others including methyl benzoylformate; 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime; 4,4,4-(hexyamethyltriamino)triphenyl methane; 2-benzyl-2-dimethylamino-4-morpholinobutyrophenone; 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one; 4,4-bis(diethylamino)benzophenone; 2-ethyl anthraquinone; and the like.

Polymeric photoinitiators are also suitable, including, for example, polymeric aminobenzoates (GENOPOL AB-1 from Rahn, Omnipol ASA from IGM or Speedcure 7040 from Lambson), polymeric benzophenone derivatives (GENOPOL BP-1 from Rahn, Omnipol BP from IGM or Speedcure 7005 from Lambson), and polymeric thioxanthone derivatives (GENOPOL TX-1 from Rahn, Omnipol TX from IGM or Speedcure 7010 from Lambson).

An amine synergist may also be included in the ink formulation. Suitable examples include, but are not limited to, the following: ethyl-4-(dimethylamino)benzoate; 2-ethylhexyl-4-(dimethylamino)benzoate; 2-(dimethylamino)ethylbenzoate; poly[oxy(methyl-1,2-ethanediyl)]; α-[4-(dimethylamino)-α-butoxy; butoxyethyl-4-(dimethylamino)benzoate; plus EBECRYL 80/81/83, EBECRYL LEO 10551/10552/10553, EBECRYL 7100 and EBECRYL P116 available from Cytec; CN501, CN503, CN550, CN UVA421, CN341, CN3705, CN3715, CN3735, CN3755, CN381, CN384, CN584, and CN554 all available from Sartomer; GENOMER 5142, GENOMER 5161, and GENOMER 5275 from Rahn; PHOTOMER 4771, PHOTOMER 4779F, PHOTOMER 4967F, PHOTOMER 4968F, PHOTOMER 5006F, PHOTOMER 4775F, PHOTOMER 5960F, LAROMER LR8996, LAROMER PO 94F and LAROMER P077F, all available from BASF; OMNIRAD CI-250 and OMNILANE A1230C from IGM Resins; and DESMOLUX VPLS 2299 from Bayer Coatings.

Defoamers can also optionally be included in the formulation, which prevent the formation of foam during manufacture of the ink, and also while printing. Examples of suitable defoamers include TEGO FOAMEX N, FOAMEX 1488, 1495, 3062, 7447, 800, 8030, 805, 8050, 810, 815N, 822, 825, 830, 831, 835, 840, 842, 843, 845, 855, 860, and 883, TEGO FOAMEX K3, TEGO FOAMEX K7/K8 and TEGO TWIN 4000, all available from Evonik. Available from Byk is BYK-066N, 088, 055, 057, 1790, and 020, BYK-A 530, and 067A, and BYK 354.

Surface control additives are often optionally used to control the surface tension of the ink, which is required to adjust the wetting of the substrate. They can also be used to control the level of slip and scratch resistance of the coating. Examples of suitable surface control additives include but are not limited to TEGO FLOW300, 370, and 425, TEGO GLIDE 100, 110,130, 406, 410, 411, 415, 420, 432, 435, 440, 482, A115, and B1484, TEGO GLIDE ZG 400, TEGO RAD2010, 2011, 2100, 2200N, 2250, 2300, 2500, 2600, 2650, and 2700, TEGO TWIN 4000, and 4100, TEGO WET 240, 250, 260, 265, 270, 280, 500, 505, and 510 and TEGO WET KL245, all available from Evonik. Available from Byk are BYK 333 and 337, BYK UV3500, BYK 378, 347, and 361, BYK UV3530, and 3570, CERAFLOUR 998 and 996, NANOBYK 3601, 3610, and 3650 and CERMAT 258. Available from Cytec are EBECRYL 350 and 1360, MODAFLOW 9200, and EBECRYL 341. From Sartomer, the aliphatic silicone acrylate CN9800 may be used.

The ink compositions of the present invention may optionally contain one or more colorants, including pigments and/or dyes, solid fillers, and solid waxes. Examples of suitable organic or inorganic pigments include, but are not limited to, carbon black, zinc oxide, titanium dioxide, phthalocyanine, anthraquinones, perylenes, carbazoles, monoazo and disazobenzimidazoles, rhodamines, indigoids, quinacridones, diazopyranthrones, dinitroanilines, pyrazoles, diazopyranthrones, dianisidines, pyranthrones, tetracholoroisoindolines, dioxazines, monoazoacrylides and anthrapyrimidines. The dyes include, but are not limited to, azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, combinations thereof, and the like.

Commercial organic pigments classified according to Color Index International may be used, according to the following trade designations: blue pigments PB1, PB15, PB15:1, PB15:2, PB15:3, PB15:4, PB15:6, PB16, PB60; brown pigments PBS, PB23, and PB265; green pigments PG1, PG7, PG10 and PG36; yellow pigments PY3, PY14, PY16, PY17, PY24, PY65, PY73, PY74 PY83, PY95, PY97, PY108, PY109,PY110, PY113, PY128, PY129,PY138, PY139, PY150, PY151, PY154, PY156, PY175, PY180 and PY213; orange pigments PO5, PO15, PO16, PO31, PO34, PO36, PO43, PO48, PO51, PO60, PO61 and PO71; red pigments PR4, PRS, PR7, PR9, PR22, PR23, PR48, PR48:2, PR49, PR112, PR122, PR123, PR149, PR166, PR168, PR170, PR177, PR179, PR190, PR202, PR206, PR207, PR224 and PR254: violet pigments PV19, PV23, PV32, PV37 and PV42; black pigments PBk1, PBk6, PBk7, PBk8, PBk9, PBk10, PBk11, PBk12, PBk13, PBk14, PBk17, PBk18, PBk19, PBk22, PBk23, PBk24, PBk25, PBk26, PBk27, PBk28, PBk29, PBk30, PBk31, PBk32, PBk33, PBk34, PBk35, NBk1, NBk2, NBk3, NBk4, NBk6; combinations thereof, and the like.

Other non pigmentary solids may be optionally included, which may include waxes. Examples would include, but are not limited to, calcium carbonate, clays, silicates, silicas, polyolefin and polyamide powders, and talcs. Non pigmentary powders may be present in the range 1-25%.

The pigments, fillers and waxes are milled or dispersed to typically less than 10 micrometers with a preferred particle size distribution of 0.2-15 microns, more preferably 0.2-12 microns dependent on application. The pigment dispersion will typically contain 20-40% pigment, monomer which can be a mono or multifunctional (meth)acrylate monomer, with added stabilizer, inhibitor, dispersant and optionally a pigment additive/synergist and/or a wetting additive/oligomer/resin. The ratio of pigment to dispersant would usually be 1:2 to 9:1 depending on the chemistry of the pigment and dispersant. Typical dispersants would include EFKA 7414, 7476, 7477, 7700, 7701, 7702, 7710, 7731 and 7732 available from BASF and SOLSPERSE 1700, 1900, 24000SC/GR, 26000, 32000, 33000, 35000, 36000, 39000, 41000 and 71000 available from Lubrizol. Examples of additive/synergists to aid dispersion stability include SOLSPERSE 5000, 12000 and 22000 from Lubrizol.

The curing of the inks of the present invention normally requires a traditional mercury vapor discharge lamp to generate UV radiation for initiating the cure of energy curable screen inks. Solid state UV radiation sources such as UV light emitting diodes (LEDs) can also be used as the source of UV radiation. Mercury lamps also take time to heat up and cool down and have the potential to release mercury, which is highly toxic. UV LEDs can be rapidly switched on and off, are more energy efficient and don't generate heat, so are better for use with heat sensitive substrates. The inks of the present invention could also be formulated to cure by other radiation sources, such as for example microwave, infrared, electron beam, visible light, x-ray, etc.

EXAMPLES

The following examples illustrate specific aspects of the present invention and are not intended to limit the scope thereof in any respect and should not be so construed.

EXAMPLE 1

Properties of cyan screen printing ink composition containing diacetone acrylamide

Cyan screen inks were prepared according to the formulations in Table 1, using a rotor-stator (Silverson) mixer.

TABLE 1 Process Cyan Screen Graphic printing ink formulations 1A-1G suitable for printing onto a range of substrates Formulation Cyan Cyan Cyan Cyan Cyan Cyan Cyan Material Description 1A 1B 1C 1D 1E 1F 1G N-vinyl caprolactam BASF, V-CAP 8.6 Diacetone acrylamide Sigma-Aldrich 8.6 Ethoxyethoxy ethyl acrylate Sartomer SR256 5.8 5.8 5.8 14.4 5.8 5.8 5.8 N-isopropyl acrylamide Sigma-Aldrich 8.6 Acryloyl morpholine RAHN, ACMO 8.6 1,6 Hexanediol diacrylate Sartomer SR238 8.6 Cyclic trimethylolpropane formal acrylate Sartomer, SR531 27.7 27.7 27.7 27.7 27.7 27.7 36.3 Stabilizer Rahn, Genorad 16 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Photoinitiator IGM, Omnirad TPO 2.3 2.3 2.3 2.3 2.3 2.3 2.3 Photoinitiator Rahn, Genocure MBF 3.8 3.8 3.8 3.8 3.8 3.8 3.8 Resin BASF, Laropal A81 16.3 16.3 16.3 16.3 16.3 16.3 16.3 Filler Omya, Omnicarb 21.1 21.1 21.1 21.1 21.1 21.1 21.1 Extra GU Wax additive powder Ceridust 3620 6.7 6.7 6.7 6.7 6.7 6.7 6.7 Fumed Silica Degussa, Aerosil 300 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Pigment concentrate containing 30% CI 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Pigment Blue 15:4 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Printing Ink Testing:

The screen ink printable compositions 1A-1G were printed using a 150T mesh screen onto 240 micron white rigid PVC and cured using a Natgraph, two lamp medium pressure mercury ultra-violet curing unit, with 250 mJ/cm² per layer exposure. The resulting prints were tested for cross-hatch adhesion according to ISO 2409 and also for pencil hardness, as described in ISO 15184 (2012). The results are displayed below in Table 2.

Viscosities of the printing compositions were measured using an REL cone and plate viscometer, large cone speed 2 at 25° C. and were found to be in the range 0.9-1.4 Pa s.

TABLE 2 Adhesion and pencil hardness for Cyan Examples 1A-1G No of Cross-hatch Pencil Formulation Layers Tape* Hardness Cyan 1A 1 0 H Cyan 1A 4 0 HB Cyan 1B 1 0 H Cyan 1B 4 3 B Cyan 1C 1 0 HB Cyan 1C 4 0 HB Cyan 1D 1 3 B Cyan 1D 4 5 3B Cyan 1E 1 0 HB Cyan 1E 4 5 HB Cyan 1F 1 0 H Cyan 1F 4 0 H Cyan 1G 1 0 H Cyan 1G 4 0 B Cross-hatch tape adhesion is assessed as follows: 0 = no removal; 1 = 5-15% removal; 2 = 16-30% removal; 3 = 31-45% removal; 4 = 46-64% removal; 5 = greater than 64% removal. Pencil hardness: 3B < B < HB < H (i.e. H is the hardest result here)

The results in Table 2 demonstrate that the Inventive Cyan 1A, containing the diacetone acrylamide, has faster cure speed than the other acrylamides tested,andComparative Example 1B and 1E, including the well-known and widely used tertiary acrylamide ACMO, and has better performance than N-vinyl caprolactam (Comparative Example 1C) with respect to improved single layer pencil hardness and scratch adhesion. The invention therefore shows excellent utility. Formulations 1D and 1G contain no acrylamide or N-vinyl caprolactam and show very poor hardness in multi-layers. Formulation 1F has good performance, but contains the di-functional monomer HDDA and has reduced impact resistance (see below).

Impact Resistance

The printing ink compositions Cyan 1A-1G were printed using a 150T mesh on 220 micron clear rigid PVC, with steps of 1 to 4 layers on both sides, cured using a Natgraph medium pressure mercury ultra-violet curing unit, with 250 mJ/cm² per layer. The 4×4 layer build was impact tested using a Sheen impact tester with a 1 kg semi-circular impacter, with drop heights of 40 cm and 60 cm, see Table 3 below. These tests are comparative in nature.

TABLE 3 Impact Resistance for Cyan Examples 1A-1G Formulation Drop height 40 cm Drop height 60 cm Cyan 1A FILM OK FILM OK Cyan 1B FILM OK FILM OK Cyan 1C FILM OK FILM OK Cyan 1D FILM OK FILM OK Cyan 1E FILM OK FILM OK Cyan 1F FILM BREAKS FILM BREAKS Cyan 1G FILM OK FILM OK OK = printed substrate dented/deformed, but intact with no breaks. Film breaks = in places both ink film and substrate shattered.

The results in Table 3 demonstrate that the Inventive Cyan 1A, containing the diacetone acrylamide, has similar impact resistant performance to N-vinyl caprolactam and shows similar or better performance than all the other acrylamides tested. The impact resistance is greatly reduced in formulation 1F due to the presence of di-functional monomer (HDDA). Formulation 1F will not even survive an impact of 5 cm without shattering

Squeegee Swelling

The squeegee swelling tendencies of printing ink compositions Cyan 1A-1G were assessed by an internally developed test, where a 2 g drop of ink of diameter 15 mm is dispensed onto the test rubber squeegee and left for 24 hours at 20° C. After the test expired the ink was cleaned off and the effect on the squeegee measured with a digital micrometer. The amount of swelling was calculated as final thickness—initial thickness. The results are recorded in Table 4 below.

TABLE 4 Squeegee swelling Swelling microns Swelling microns Formulation Marathon Red TS Printmor Green Cyan 1A 60 53 Cyan 1B 105 78 Cyan 1C 90 76 Cyan 1D 90 66 Cyan 1E 67 52 Cyan 1F 62 46 Cyan 1G 62 46

The results in Table 4 demonstrate that the Inventive Cyan 1A, containing the diacetone acrylamide, gives good performance in this squeegee swelling test, particularly on laminated squeegees like Marathon Red. Formulation 1B and 1C containing ACMO and NVC are particularly poor. It is to be noted the laminated construction squeegees like the Marathon Red are often more susceptible to swelling than the single layer constructions like Printmor.

Adhesion

The inks in Table 1 were printed onto Priplac sheet polypropylene, Correx fluted polypropylene, polycarbonate, rigid polystyrene, rigid vinyl and flexible vinyl substrates using a 150T mesh and cured at a dose of 250 mJ/cm² under a medium pressure mercury arc lamp on a Natgraph UV rig. Their adhesion to the test substrates was then tested with the cross-hatch adhesion test (ISO 2409) using a cutter and Tessa adhesive tape. Results are given in numerical categories according to the amount of ink removed from zero (perfect, no ink removed) to 5 (>35% ink removed). These results are given in table 5.

TABLE 5 Adhesion Crosshatch adhesion test results Poly- Fluted propylene Poly- Rigid Formulation sheet Polycarbonate propylene Polystyrene Rigid PVC Flexible vinyl Cyan 1A 0 0 0 0 0 0 Cyan 1B 0 3 0 0 1 1 Cyan 1C 1 2 0 0 0 1 Cyan 1D 1 2 1 1 3 3 Cyan 1E 0 3 0 2 3 5 Cyan 1F 0 1 0 2 0 0 Cyan 1G 0 0 0 0 0 0

The results in Table 5 demonstrate that the Inventive Cyan 1A, containing the diacetone acrylamide, can be used in screen printable formulations without any significant loss of adhesion against a typical standard formulation Cyan 1C containing NVC. It should also be noted that the Inventive Cyan 1A also has superior performance to the well-known and widely used ACMO formulation 1B. Formulation 1G is softer/more surface tack, and 1F, as previously mentioned, is not sufficiently impact resistant when printed on rigid PVC.

EXAMPLE 2

Properties of cyan screen printing ink compositions containing diacetone acrylamide

Screen printable compositions were prepared according to the formulations in Table 6 using a rotor-stator mixer. The viscosities of the resulting inks were measured using a REL cone and plate viscometer large cone speed 2 at 25° C. and found all to be in the range from 0.9-1.4 Pa s. The compositions were printed by hand through a 150T mesh on a range of plastic substrates, in single and multiple layers, and ultra-violet cured at 250 mJ/cm² per layer on a Natgraph curing unit. The adhesion of the inks was assessed using cross hatch ISO 2409 and pencil hardness, as described in ISO 15184 (2012).

TABLE 6 Cyan screen ink formulations 2H-2L. Examples 2H-2L are further variations on the 2A-2G Examples Formulation Cyan Cyan Cyan Cyan Cyan Material Description 2H 2I 2J 2K 2L N-vinyl caprolactam BASF 8.2 Cyclic trimethylolpropane Sartomer, SR531 19.3 26.1 19.3 19.3 19.3 formal acrylate N-Isopropyl acrylamide Sigma-Aldrich 8.2 2-Phenoxyethylacrylate Sartomer, SR339EU 12.5 12.5 12.5 12.5 12.5 Diacetone acrylamide Sigma-Aldrich 8.2 Ethoethoxy ethylacrylate Sartomer, SR256 3.4 4.8 3.4 3.4 3.4 Acroylol morpholine Rahn, ACMO 8.2 Photoinitiator IGM, Omnirad 73 4.8 4.8 4.8 4.8 4.8 Photoinitiator BASF, Irgacure 184 1.9 1.9 1.9 1.9 1.9 Photoinitiator IGM, Omnirad TPO 1.9 1.9 1.9 1.9 1.9 Stabilizer package Rahn, Genorad 16 0.2 0.2 0.2 0.2 0.2 Aldehyde resin BASF, Laropal A81 16.3 16.3 16.3 16.3 16.3 Filler OMYA, Omnicarb 20.0 20.0 20.0 20.0 20.0 Extra GU Fumed silica Degussa, Aerosil 300 3.5 3.5 3.5 3.5 3.5 Wax powder Ceridust 3620 4.0 4.0 4.0 4.0 4.0 Pigment dispersion 30% PB Internal 4.0 4.0 4.0 4.0 4.0 15:4 Total 100.0 100.0 100.0 100.0 100.0

Adhesion and Pencil Hardness

The results in Table 7 demonstrate that the Inventive Cyan 2K, containing the diacetone acrylamide, is as effective as N-vinyl caprolactam in formulation 2H. The acrylamides N-acryloyl morpholine and isopropyl acrylamide contained in compositions 2J and 2L result in inferior performance.

TABLE 7 Adhesion and Pencil Hardness of Cyan Examples 2K-2L No of Cross-hatch Pencil Formulation Layers Tape Hardness Cyan 2H 1 0 H-F Cyan 2H 4 0 HB Cyan 2I 1 3 HB Cyan 2I 4 5 3B Cyan 2J 1 0 B Cyan 2J 4 3 B Cyan 2K 1 0 H Cyan 2K 4 0 HB Cyan 2L 1 1 B Cyan 2L 4 5 B Cross-hatch tape adhesion is assessed as follows: 0 = no removal; 1 = 5-15% removal; 2 = 16-30% removal; 3 = 31-45% removal; 4 = 46-64% removal; 5 = greater than 64% removal Pencil hardness: 3B < B < HB < F < H

EXAMPLE 3

Properties of white screen inks containing diacetone acrylamide

White screen printing compositions were prepared according to the formulations in Table 8. The components were premixed, followed by triple-roll milling until the dispersion grind was less than 10 microns. The resulting inks were measured on a REL cone and plate viscometer with a small cone speed 2 at 25° C. The ink viscosities were measured and found to be all in the range 1.8-2.5 Pa s.

TABLE 8 White screen formulations 3A-3E Formulation Material Description White 3A White 3B White 3C White 3D White 3E N-vinyl caprolactam BASF, V-CAP 9.8 Diacetone acrylamide Sigma-Aldrich 9.8 Tetrahydro furfuryl acrylate Sartomer SR285 7.5 7.5 7.5 7.5 7.5 Isopropyl acrylamide Sigma-Aldrich 9.8 Isobornyl acrylate Sartomer, SR506D 9.7 9.7 9.7 9.7 9.7 Acroylol morpholine Rahn 0 9.8 0 0 0 Photoinitiator IGM, Omnirad TPO 3.8 3.8 3.8 3.8 3.8 Photoinitiator Omnirad 73 2.0 2.0 2.0 2.0 2.0 Dispersant Lubrizol Solsperse 0.6 0.6 0.6 0.6 0.6 41000 Photoinitiator BASF, Irgacure 819 0.5 0.5 0.5 0.5 0.5 De-foamer SAG 100E 0.8 0.8 0.8 0.8 0.8 Resin oligomer Solmer 20.0 20.0 20.0 20.0 20.0 SU5225 Stabilizer package Rahn 0.3 0.3 0.3 0.3 0.3 Genorad 16 Pigment Tioxide TR52 40.0 40.0 40.0 40.0 40.0 Filler Spacerite ONS 5.0 5.0 5.0 5.0 5.0 2-(2-vinyloxyethoxy)ethyl VEEA Nippon Shokubai 9.8 acrylate Total 100.0 100.0 100.0 100.0 100.0

Print Testing of the Ink Formulations

The white ink formulations from Table 8 were printed using a 140T mesh screen onto clear sheet substrates, polycarbonate, polyester and rigid polyvinyl chloride and ultra-violet cured using a Natgraph unit with 120 W/cm medium pressure mercury lamps. The resulting prints were assessed for cross hatch adhesion using ISO 2409 and also pencil scratch hardness, as described in ISO 15184 (2012). Two sets of prints were produced, on Autostat CT3 100 micron polyester clear sheet, one set with an exposure of 650 mJ/cm² and the second with 2000 mJ/cm². The prints were each cut into two parts, one part was aged for a week at 22° C., the other was placed in an environmental chamber (SANYO ATMOS) and the prints stored at 105° C. for 7 days. The two sets of prints were assessed for thermal/ultra violet induced yellowing by comparing the room temperature stored prints with the 105° C. stored prints using an X-Rite Spectro-Eye photo-spectrometer. The yellowing was measured in terms of a delta E difference average over 5 measurements. The results are recorded in Table 9 below.

TABLE 9 Yellowing Exposure Yellowing Exposure Yellowing Formulation mJ/cm2 Delta E mJ/cm2 Delta E White 3A 650 1.99 2000 3.83 White 3B 650 1.07 2000 1.92 White 3C 650 0.92 2000 1.49 White 3D 650 1.10 2000 1.88 White 3E 650 1.39 2000 2.69

The results in Table 9 demonstrate that the formulation White 3C, which contains the material diacetone acrylamide is clearly and surprisingly the most resistant to both thermal and UV/thermal yellowing. The formulation White 3A, containing N-vinyl caprolactam is very poor in this respect. Also formulation White 3B and White 3D containing ACMO and isopropyl acrylamide were found to be clearly both inferior to White 3C.

Substrate Adhesion and Thermoforming

The adhesion as previously explained was assessed for the test formulations using cross hatch tape and a pencil hardness tester on prints cured with 650 mJ/cm² per layer using a Natgraph ultra-violet curing unit.

Thermoforming was conducted using a Clarke vacuum Former 725 FLB model on 240 micron clear rigid PVC prints, which were prepared by printing the formulations White A-E through a 140T screen, cured with 650 mJ/cm² on a Natgraph ultra-violet curing unit. The forming was measured using a mold requiring a coating capable of extending 300 per cent. The results of both the adhesion tests and forming are shown in Table 10. The cross hatch tape results are not recorded as all the formulations using the test had perfect adhesion (0) with no removal and therefore the results were non-discriminatory.

TABLE 10 Hardness and thermoforming Pencil Pencil Pencil hardness hardness hardness Formulation Polycarbonate Rigid PVC Polyester Thermo- number 240 microns 240 microns 100 microns forming White 3A H F-H H FORMS White 3B H H H FORMS White 3C F H H FORMS White 3D F H H FORMS White 3E F H H CRACKS The rating “Forms” means that the printed substrate stretches and deforms with no splits or holes in extended ink or substrate. The term “Cracks” means the ink film splits on extension with gaps, the substrate may or may not be split.

The formulation White 3C, containing diacetone acrylamide, showed good adhesion and formability, and was slightly softer than formulations White 3A and White 3B when printed on polycarbonate, which are based on White 3A (N-vinyl caprolactam), and White 3B acrylol morpholine. Formulation White 3E is incapable of extension and cracks both the ink and underlying substrate. As mentioned previously formulation White 3C is best for retaining whiteness without yellowing on storage of inks or printed parts.

EXAMPLE 4

First down narrow web white rotary screen/flexographic ink containing diacetone acrylamide

White printing compositions were prepared according to the formulations in Table 11. The components were premixed, followed by triple roll milling until the dispersion grind was less than 10 microns. The resulting inks were measured on an REL cone and plate viscometer with a large cone, speed 2 at 25° C. The ink viscosities were measured and found to be in the range 0.6-0.8 Pa s.

TABLE 11 White Ink Formulations 4A-4E Formulation Material Description 4A 4B 4C 4D 4E N-vinyl caprolactam BASF, V-CAP 9.6 Diacetone acrylamide Sigma-Aldrich 9.6 Isopropyl acrylamide Sigma-Aldrich 9.6 N-acryloyl morpholine Rahn, ACMO 9.6 Isobornyl acrylate Sartomer, SR506D 4.7 4.7 4.7 4.7 4.7 Cyclic trimetylolpropane formal Sartomer SR 531 9.6 Di-trimethyolpropantetra acrylate Allnex, Ebecryl 40 5.0 5.0 5.0 5.0 5.0 Photoinitiator IGM, Omnirad 73 1.8 1.8 1.8 1.8 1.8 Photoinitiator IGM, Omnirad TPO 3.3 3.3 3.3 3.3 3.3 Photoinitiator BASF, Irgacure 819 0.5 0.5 0.5 0.5 0.5 De-foamer Byk, A501 1.1 1.1 1.1 1.1 1.1 Resin/oligomer Allnex, Ebecryl 3701 21.3 21.3 21.3 21.3 21.3 Stabilizer package Rahn, genorad 16 0.2 0.2 0.2 0.2 0.2 Pigment white Kronos, 2035 45.0 45.0 45.0 45.0 45.0 Hexandiol diacrylate Sartomer SR 238 7.5 7.5 7.5 7.5 7.5 Total 100.0 100.0 100.0 100.0 100.0

TABLE 12 Adhesion and maximum cure speed Formulation Substrate Maximum cure speed mJ/cm² 4A Baker, PP top coated 200 4B Baker, PP top coated 330 4C Baker, PP top coated 170 4D Baker, PP top coated 200 4E Baker, PP top coated 500

The Example 4 white formulations were printed using a 140T mesh screen on 80 micron gauge top coated polypropylene substrate and cured using a Natgraph unit with medium pressure 120 W/cm lamps. The resulting prints were assessed for cross hatch adhesion using ISO 2409 and the maximum cure speed, as indicated by the minimum energy required to achieve full adhesion (no removal (0)), and the results are recorded above in Table 12. It is to be noted the formulations in Table 11 are of suitable rheology to be applied via rotary screen, flexographic or bar coating machines. The results show formulation 4D containing the material diacetone acrylamide has similar cure speed and adhesion to formulation 4A, containing acrylol morpholine (ACMO) and slightly less than the standard formulation 4C containing N-vinylcaprolactam. Formulations 4B and 4E were much slower with poorer adhesion.

TABLE 13 Odor and discoloration of Example 4 formulations Odor after 7 Initial Visual color days at 80° C. Initial Odor Formulation after 7 days (1 best, Visual (1 best, number at 80° C. 5 worst) Color 5 worst) 4A White 3 White 2/3 4B White 3 White 3 4C Cream 4/5 White 3/4 4D White 2 White 2 4E White 2 White 2

Small aluminum containers containing 50 g each of the above formulations were stored in an oven at 80° C. to simulate aging of the formulations with time. The initial color and odor were assessed by humans with the odor rated against three criteria: intensity; pleasantness/unpleasantness; and persistence, on an arbitrary scale 1-5 (1=best, and 5=worst). The average is recorded in Table 13. Over the 7 day storage period formulations 4A, 4B, 4D and 4E remained white, while formulation 4C based on N-vinylcaprolactam became a yellowish cream. The inventive diacetone acrylamide incorporated in formulation 4D had an initial low acrylate odor, which did not increase on storage. Formulation 4E followed a similar pattern and contains isopropyl acrylamide, which was previously found to have poor cure speed and adhesion. Formulation 4C containing N-vinylcaprolactam had an initially high unpleasant odor which increased markedly on storage. Both formulations 4A and 4B had higher odor than 4D, but not as strong as 4C.

EXAMPLE 5

First down white flexographic ink containing diacetone acrylamide

White printing compositions were prepared according to the formulations in Table 14. The components were high speed mixed using a rotor stator (Silverson mixer) until the dispersion grind was less than 10 microns. The resulting inks were measured on an REL cone and plate viscometer with a large cone, speed 2 at 25° C. The ink viscosities were measured and found to be in the range 0.3-0.4 Pa s. Example 5C and 5E are inventive, Examples 5A, 5B and 5D are comparative.

TABLE 14 White Ink Formulations 5A-5E Formulation Material Description 5A 5B 5C 5D 5E N-vinyl caprolactam BASF, V-CAP 6.0 Diacetone acrylamide Sigma-Aldrich 6.0 6.0 Phenoxy ethyl acrylate Miramer M140 6.0 N-acryloyl morpholine Rahn, ACMO 6.0 Hexandiol diacrylate Sartomer, SR 238 16.9 16.9 16.9 16.9 13.9 Stabiliser package Rahn Genorad 16 0.2 0.2 0.2 0.2 0.2 De-foamer Byk A501 1.1 1.1 1.1 1.1 1.1 Photoinitiator IGM, Omnirad 73 3.2 3.2 3.2 3.2 3.2 Photoinitiator IGM, Omnirad TPO 3.5 3.5 3.5 3.5 3.5 Photoinitiator BASF, Irgacure 819 0.8 0.8 0.8 0.8 0.8 Resin/oligomer Sartomer CN111 4.0 4.0 4.0 4.0 4.0 Resin/oligomer Allnex, Ebecryl 3701 10.7 10.7 10.7 10.7 10.7 Pigment white Tioxide TR 52 Huntsman 52.0 52.0 52.0 52.0 52.0 Dispersant Solsperse 41000 1.6 1.6 1.6 1.6 1.6 Ethoxypropanol Dow Chemicals 3.0 Total 100.0 100.0 100.0 100.0 100.0

TABLE 15 Adhesion and maximum cure speed Formulation Substrate Maximum cure speed mJ/cm² 5A Ritrama, PP top coated 100 5B Ritrama, PP top coated 80 5C Ritrama, PP top coated 80 5D Ritrama, PP top coated 80 5E Ritrama, PP top coated 80

The Example 5 white formulations were hand coated using a yellow coating bar (3-4 microns) on 80 micron gauge top coated polypropylene substrate and cured using a Natgraph unit with medium pressure 120 W/cm lamps. The resulting prints were assessed for cross hatch adhesion using ISO 2409 and the maximum cure speed, as indicated by the minimum energy required to achieve full adhesion (no removal (0)), and no initial surface tack or fingernail scratch. The results were assessed and recorded above in Table 15. It is to be noted that the formulations in Table 14 are of suitable rheology to be applied via flexographic or bar coating machines. The results show the inventive examples 5C and 5E containing the material diacetone acrylamide have faster cure speed and better scratch adhesion/resistance than the comparative example 5A, containing phenoxyethyl acrylate (PEA), and are similar to the examples 5B containing n-vinyl caprolactam (NVC) and 5D containing acrylolmorpholine (ACMO). Example formulations 5B, 5C, 5E and 5D had good cross-hatch adhesion and surface cure even at 55 mJ/cm2 exposure.

The present invention has now been described in detail, including the preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on this invention that fall within the scope and spirit of the invention. 

1. A radiation curable printing ink or coating composition comprising: 1-60% wt. of an acrylamide material or blends thereof, wherein at least a portion of the acrylamide material is diacetone acrylamide; 1-60% wt. of an additional monofunctional acrylate or methacrylate monomer or blends thereof; 0-20% wt. of a difunctional acrylate or methacrylate monomer or blends thereof; 0-10% wt. of a trifunctional or higher acrylate or methacrylate monomer or blends thereof; 0-60% wt. of a mono or multifunctional acrylate or methacrylate oligomer or blends thereof; 0-40% wt. additional reactive oligomers or resins; 0-40% wt. additional inert oligomers or resins; 0-25% wt. of a photoinitiator or blends thereof; 0-5% wt. water; and 0-5% wt. solvent; wherein, the composition contains a maximum of 5% wt. N-vinyl compounds; and wherein the composition contains no N-vinyl caprolactam, N-vinyl pyrrolidone, or N-acryloyl morpholine.
 2. The composition of claim 1, wherein the majority of the acrylamide material is diacetone acrylamide.
 3. The composition of claim 1, wherein all of the acrylamide material is diacetone acrylamide.
 4. The composition of claim 1 containing no N-vinyl compounds.
 5. The composition of claim 1, wherein the additional monofunctional acrylate or methacrylate monomer comprises a cyclic mono-functional (meth)acrylate, with the cyclic radical being either saturated or unsaturated, including aromatic.
 6. The composition of claim 1, wherein the additional monofunctional acrylate or methacrylate monomer is selected from the group consisting of phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), isobornyl acrylate (IBOA), t-butyl cyclohexyl acrylate, 3,3,5-trimethyl cyclohexyl acrylate, tetrahydro-furfuryl acrylate (THFA), or mixtures thereof.
 7. The composition of claim 1, containing no added water.
 8. The composition of claim 1, containing monofunctional monomers in an amount of 1-45% wt.
 9. The composition of claim containing difunctional or higher monomers in an amount of 0-15% wt.
 10. The composition of claim 1, wherein the photoinitiator is present in an amount of 0.1-20% wt.
 11. The composition of claim 1, wherein the acrylamide material is present an amount of 1-40% wt.
 12. The composition of claim 1, wherein the acrylamide material is present in an amount of 1-30% wt.
 13. The composition of claim 1, wherein the acrylamide material is present in an amount of 1-20% wt.
 14. The composition of claim 1, wherein the acrylamide material is present in an amount of 1-10% wt.
 15. The composition of claim 1, wherein the acrylamide material is present in an amount of 1-5% wt.
 16. The composition of claim 1, further comprising a colorant or filler.
 17. The composition of claim 1, further comprising one or more additives selected from the group consisting of stabilizers, surfactants, defoamers, slip additives, waxes, wetting additives and synergists.
 18. A composition according to claim 1, that is a screen printable ink or coating, and is suitable for flat-bed or rotary screen printing.
 19. The composition of claim 18, having a viscosity in the range 0.2-2.5 Pa s, measured on a cone and plate viscometer at 25° C.
 20. A composition according to claim 1, that is a flexographic ink or coating.
 21. The composition of claim 20, having a viscosity in the range of 0.2-1.0 Pa s, measured on a cone and plate viscometer at 25° C.
 22. A composition according to claim 1, that is a gravure, pad or spray ink or coating.
 23. The composition of claim 22, having a viscosity in the range of 0.01-0.2 Pas at 25° C.
 24. A radiation curable printing/coating composition, according claim 1, which, when cured, is impact resistant, extensible, and has good adhesion to a range of substrates when printed in single or multiple layers.
 25. A radiation curable printing/coating composition, according to claim 1 with good storage stability with respect to yellowing and odor generation.
 26. A radiation curable printing ink or coating composition, according to claim 1, with low swelling of ink printing components, particularly rubber squeegees, plates, rollers etc.
 27. A method of making an energy curable printing ink or coating composition comprising mixing: 1-60% wt. of an acrylamide material or blends thereof, wherein at least a portion of the acrylamide material is diacetone acrylamide; 1-60% wt. of an additional monofunctional acrylate or methacrylate monomer or blends thereof; 0-20% wt. of a difunctional acrylate or methacrylate monomer or blends thereof; 0-10% wt. of a trifunctional or higher acrylate or methacrylate monomer or blends thereof; 0-60% wt. of a mono or multifunctional acrylate or methacrylate oligomer or blends thereof; 0-40% wt. additional reactive oligomers or resins; 0-40% wt. additional inert oligomers or resins; 0-25% wt. of a photoinitiator or blends thereof; 0-5% wt. water; and 0-5% wt. solvent; wherein, the composition contains a maximum of 5% wt. N-vinyl compounds; and wherein the composition contains no N-vinyl caprolactam, N-vinyl pyrrolidone, or N-acryloyl morpholine.
 28. A printed article comprising the radiation curable ink or coating composition of claim
 1. 